1. Properties of Light Parkland Junior High School 2012-2013

2. What is Light? Simply stated, light is the form of energy you can see. This energy can be produced naturally by the sun or fire, or artificially by light- producing technologies, like batteries. Radiation is the wave like transfer of light from its source in all directions. Light is often called radiant energy. Light from the sun is formed by nuclear fusion.

3. What is Light? Light sources are luminous or illuminated. Luminous objects produce their own light and can be either artificial or natural. Illuminated objects do not produce light but are seen because they reflect light from another object.

4. Light Intensity The amount of energy a surface receives depends on the intensity of the light. The more intense the light, the more light can be absorbed.

5. Types of Light Incandescent light is light that is so hot it glows –Examples: candles, fire, incandescent light bulbs etc Luminescent sources of light do not need to be hot to glow. –Examples: fireflys, glow in the dark toys, fluorescent light bulbs

6. Sources of Light - Artificial

7. Incandescent Light Dictionary.com –Emitting light as a result of being heated. –(of an electric light) Containing a filament that glows white-hot when heated by a current passed through it. Electrical energy →→Thermal energy →→ Visible light energy

8. Fluorescent Light Ultraviolet light is absorbed by fabric particles, which in turn emit some of the energy as light – glowing Ultraviolet light energy→→ Energy absorbed by particles →→ Visible light energy This form of light does not give off heat.

9. Phosphorescent Light light energy is stored and released later as visible light For example, glow in the dark toys that glow after all light has been removed.

10. Chemiluminescent Light light energy released by chemical reactions These chemical reactions produce light but not heat.

11. Sources of Light - Natural

12. Bioluminescent Light Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". This type of light is a form of chemiluminescent light.

13. First Property of Light The first basic property of light is that light is a form of energy. Energy radiates from the Sun in all directions. When light reaches a surface, it can be absorbed and transformed into other types of energy.

14. When light reaches a surface, it can be absorbed and transformed into other types of energy… … into electrical energy Solar cells change light into electricity

15. When light reaches a surface, it can be absorbed and transformed into other types of energy… … into thermal energy Cameras change light into thermal images

16. When light reaches a surface, it can be absorbed and transformed into other types of energy… … into chemical energy Trees convert light energy into food (chemical energy)

17. Second Property of Light The second basic property of light is that it travels in a straight line from its source. Light travels at a speed of about 300,000 km per second. Until light strikes something, it will continue to travel in straight lines away from the source. The light will react in different ways depending on the substance it hits.

18. When light strikes…. When light hits clear substances such as air and water, it passes through them. These substances are transparent. If the surface is transparent, the light continues in a straight path through the object.

19. When light strikes…. A substance that lets some light pass but the light is scattered from it’s straight path is called translucent. If the surface is translucent the light will be diverted (refracted) after it passes through Frosted glass and cloudy water are translucent substances.

20. When light strikes…. A material that does not let any light pass through is called opaque. If the surface is opaque, the light will be blocked and not allowed through the object. A door is an example of an opaque substance.

21. Reflections Light sources are luminous or illuminated. Luminous objects produce their own light and can be either artificial or natural. Illuminated objects do not produce light but are seen because they reflect light from another object.

22. Reflection con’t Reflection occurs when light bounces off a surface.

25. Properties of Light - recap 1. Light is a form of energy. 2. Light travels in a straight line. 3. Light can be separated into different colours.

26. When light strikes…. When light hits clear substances such as air and water, it passes through them. These substances are transparent. A substance that lets some light pass but the light is scattered from it’s straight path is called translucent. A material that does not let any light pass through is called opaque.